Whether the connector is for optical fibers or electrical conductors, or other filaments, it is important that dirt or other foreign matter be kept from the mating surfaces since it can increase attentuation and prevent complete mating.
In order to prevent the ingress of dirt, it is usual to provide a cap which fits over the end surface of the connector when the latter is not in use. The cap itself must be kept clean when it is not in use. It has been proposed to have the caps of the mating connectors secured by chains to their respective connectors and fitted together after the connectors themselves have been connected together. This is not entirely satisfactory since, in the field, operators sometimes forget to connect the caps together. Also, the chain sometimes snags when the cable is being drawn through cavities or undergrowth. Sometimes the chain breaks and the cap gets lost, with the consequence that the connector itself then gets dirty.